A protein concentration (flare) and a cell number density in an anterior chamber of an eye reflect conditions of various disorders including a postoperative inflammation. Quantitative measurement of these is of clinical importance. As a method for measuring them quantitatively is known a method of irradiating an anterior ocular segment of an examinee with a laser light beam from a laser light source, receiving at a light receiving unit scattered light of the laser light beam from the anterior ocular segment, converting it into an electric signal, and deriving optical characteristics of the anterior ocular segment from this electric signal.
As a measurement device for use in such a measurement method is known an ophthalmic measurement device provided with a monitor photographing unit, receiving at the monitor photographing unit a virtual image of scattered light of a laser light beam emitted to an examinee's eye by a surface of a cornea, and the scattered light of the laser light beam, and carrying out a positional adjustment (alignment) between a laser light source and the photographing unit in accordance with positions of the virtual image and the scattered light at the monitor photographing unit (for example, refer to Patent Literature 1).
Also known is an ophthalmic measurement device carrying out alignment with reference to a corneal apex which is different from optical compositions of a light projecting system and a light receiving system. In the alignment, an intersecting point of optical axes of the light projecting system and the light receiving system in an examinee's eye is set as a biologic characteristic measuring point in the examinee's eye displaced as much as a predetermined distance from the corneal apex (for example, refer to Patent Literature 2).
Further known is an ophthalmic measurement device integrally provided at a measuring unit with a semiconductor laser irradiating an anterior ocular segment of an examinee's eye with a laser light beam at an angle of 30°, a high-sensitivity light receiving device receiving scattered light of a laser light beam having an angle of 60° and converting it into an electric signal, a calculating unit calculating optical characteristics of the anterior ocular segment from the electric signal, an infrared LED irradiating the examinee's eye with light from a front, a CCD photographing the examinee's eye from the front, an infrared LED irradiating the examinee's eye with light approximately at an angle of 30°, and a CCD photographing the examinee's eye at an angle of 60°. In this device, based on first and second virtual images by the two CCDs, a base is moved to adjust positional relationship between the examinee's eye and the measuring unit (for example, refer to Patent Literature 2).
In the aforementioned measurement methods, a positional adjustment (alignment) between the laser light source and the light receiving unit and the examinee's eye is important for accurate measurement of the anterior ocular segment. However, the aforementioned respective measurement devices have problems in the aforementioned accurate alignment.
For example, some of the aforementioned ophthalmic measurement devices have difficulty in increasing the accuracy of the alignment since only the reflection light at the corneal apex is referred to, and others possibly give the examinee a sense of anxiety since a position irradiated with the laser light cannot be checked. Also, in the device in which the anterior ocular segment of the examinee's eye is observed obliquely to carry out alignment, positional relationship between an examiner and the examinee differs from how the observed examinee's eye looks, which makes it difficult to operate the alignment in some cases. Further, in the device that requires alignment in two steps, there is a case in which alignment operations are complicated, which makes it difficult to shorten alignment time.